This invention relates to the field of waste water treatment machines that remove impurities and toxic materials from a water solution used in an industrial or commercial process such as dry cleaning of fabric materials, so that when removed the purified water may be returned to the ground in liquid form or to the atmosphere in the form of steam. The invention relates primarily to purifying waste water collected after use in dry cleaning equipment in which one of the chemical materials to be removed from the waste water is perchlorethylene.
Prior art of which the inventor is aware include those machines and apparatus disclosed in the following United States patents.
U.S. Pat. No. 5,266,208 discloses a system and method for cleaning waste water having at least an insoluble organic contaminant, a volatile hydrocarbon contaminant and a dissolved hydrocarbon contaminant, including the steps of forming a multiliquid phase system including an aqueous hydrocarbon-contaminated layer and isolating said aqueous hydrocarbon-contaminated layer from said multi-phase liquid system, reducing the concentration of volatile hydrocarbon contaminant by stripping and removing insoluble organic contaminant in said aqueous hydrocarbon contaminated layer by absorption to form a dissolved hydrocarbon contaminated waste water, reducing the concentration of dissolved hydrocarbon contaminant in said dissolved hydrocarbon contaminated waste water by absorption, and discharging the treated water.
U.S. Pat. No. 5,236,580 discloses a device for reclaiming dry cleaning solvent from a dry cleaning machine, comprising an evaporator, a fluid transfer mechanism to transport evaporated fluid through a filter to remove substantially all of the solvent. The solvent can also be filtered before it enters the evaporator.
U.S. Pat. No. 5,223,126 discloses a system for decontaminating dry cleaning waste water, comprising a storage tank in which a portion of the dry cleaning solvent and particulate matter settle to the bottom, a pump to pump waste water from the storage tank to first filter means to remove the remaining particulate matter and then to second filter means to remove the remaining solvent, and evaporator means to evaporate the decontaminated waste water.
U.S. Pat. No. 5,090,221 discloses a continuous water wash apparatus and method for cleaning radioactively contaminated garments, which includes a wash water system and a rinse water system, both having water polishers for removing dissolved radionucleides from the clothing.
U.S. Pat. No. 5,076,936 discloses a system for removing radioactive contaminants from liquid hazardous material such as oil, including recirculating the material between a processing tank and a filter, heating the material to increase viscosity, adding chelating agents to enhance removal of the radioactive elements, adding water in a settling tank to wash the liquid hazardous material, and passing through a pre-filter stage, mid-range filter stage and a finishing-filter stage in the outlet from the main processing tank.
U.S. Pat. No. 4,780,218 discloses a process for recovering perchlorethylene from the waste water after use in a dry cleaning machine, comprising diversion of contaminated perchlorethylene from the water separator, transferring to a still, diverting steam from a boiler through filter cartridges to strip perchlorethylene therefrom, directing such steam with perchlorethylene to the sweep input of the still and discarding excessive water from the separator.
U.S. Pat. No. 4,637,232 discloses apparatus for recycling solvent used in dry cleaning machines, comprising a predistallation unit between a main distillation chamber and a condensor, consisting of a tank to receive mingled water and solvent from the cleaning cycle which it discharges into the chamber in controlled fashion and a heat exchanger in the tank in receipt of vapor from the chamber which it channels to the condensor.
U.S. Pat. No. 4,513,590 discloses a combination filter apparatus for use with a dry cleaning machine, comprising a plurality of filter cartridges, an adsorber containing a bed of activated charcoal pellets, a condensor and a solvent-water separator mounted on a still housing. Steam is passed through the filters and charcoal bed to strip the solvent therefrom, then directed into the condensor to condense into liquid form, after which it is flowed to the water-solvent separator where the solvent condensate is separated from the water.
U.S. Pat. No. 4,354,364 discloses a dry cleaning system which captures and re-circulates portions of the cleaning solvent, such as perchlorethylene, as it is being operated.
U.S. Pat. No. 4,086,705 discloses another dry cleaning system which recovers part of the cleaning solvent during operation of the dry cleaning machine.
U.S. Pat. No. 3,451,234 discloses a liquid separator for recovering solvent from a dry cleaning machine, comprising a tank divided into two sections wherein liquid from one section can overflow the partition to the other section. A float is on one side of the partition to detect the solvent level which is flowed through a restricted outlet. On the other side of the partition is an unrestricted solvent outlet and a water outlet which determines the maximum water level.
U.S. Pat. No. 3,269,155 discloses a dry cleaning machine and separating device which as part of the drying cleaning operation and at the end of the cycle, vaporizes the cleaning solvent, blows it into a condensor where it is cooled and returned to its liquid phase, then separated from water for re-use of the solvent.